"I've never driven one of those tracks, but it would be so much different for us to go and do that - the banking, how much you lift, how you use the tyres.

"It takes us guys forever through these test days to learn how to operate these tyres in the right window, so I would imagine it's not an easy thing to do in one go.

"So it's definitely a tall order in a short space of time, but you've got one of the best drivers in the world going there.

"For sure, he will be the best driver in the paddock, but he won't have the experience any of them have. So I think it will be a very exciting challenge for him."

Jim Clark made a successful transition from Formula 1 to the Indy 500, racing there five times and winning in 1965

Alonso said: "I need to adapt very quickly. It is very challenging and it is going to be very difficult but that is exciting as well."

The Spaniard has come up with the plan with McLaren and engine partner Honda because he has an ambition to become only the second man in history after Graham Hill to win the so-called triple crown of the Monaco Grand Prix, Indy 500 and Le Mans 24 Hours.

The 35-year-old said winning this year was "not the target", but added: "At the same time, if I want to win the triple crown, one day I have to win it. So let's do it as soon as possible."

Alonso's contract with McLaren runs out this season and he said the team's desire to keep him for 2018 was not part of the discussions over Indianapolis.

"After the summer I will think and I will make a decision of what I will do next year, so nothing has changed after this discussion," he said.

"It's not that I'm thinking 'away from Formula 1'. I'm closer and closer to McLaren and to renew the contract so it's completely independent. After the summer I will see."

He added: "My commitment and my desire to win in F1 is bigger than any other challenge that I can find outside F1 so it's F1 or nothing at the moment."

Alonso is planning to visit the next IndyCar race in Alabama next weekend and have a seat fitting in the Andretti team's factory before flying to the Russian Grand Prix.

He will then spend some time on a simulator before the Spanish Grand Prix, after which he will fly direct to Indianapolis to start practice on the Monday.

Juan Pablo Montoya - also a former McLaren driver - has won the Indy500 race twice